Went out for a ride today and for some reason got a flat,but I cant figure out why. The tire has been dropping down to about 31psi if left for a few days but I checked and filled it yesterday and figured it would be ok today. It felt ok for most of my ride but when I got gas someone mentioned it was looking low and sure enough it was pretty much flat . But no holes nails or damage? Its almost done anyway, down to the wear bars in the center. I did do a small stopie (just testing brakes) but didnt come down on it very hard. I put some fix a flat stuff from a auto parts store in it and rode it home and it seems to be holding . But still have no idea why it went flat. Any ideas?